Re: Troubleshooting Techniques

Router 1.1.1.1

hostname r1.1.1.1

interface Loopback0
 ip address 1.1.1.1 255.0.0.0

interface Ethernet0
 ip address 4.0.0.1 255.0.0.0
 ip ospf message-digest-key 1 md5 cisco

!--- This command configures the MD5 authentication key
!--- on the interface as "cisco".

interface Serial0
 ip address 5.0.0.1 255.0.0.0
 clockrate 64000

!

 router ospf 2
 network 4.0.0.0 0.255.255.255 area 0
 network 5.0.0.0 0.255.255.255 area 1
 area 0 authentication message-digest

!--- This command enables MD5 authentication for area 0
!--- on the router.

 area 1 virtual-link 3.3.3.3 message-digest-key 1 md5 cisco

!--- This command creates the virtual link between Router
!--- 1.1.1.1 and Router 3.3.3.3 with MD5 authentication enabled.

Router 3.3.3.3

hostname r3.3.3.3

interface Loopback0
 ip address 3.3.3.3 255.0.0.0

interface Ethernet0
 ip address 12.0.0.3 255.0.0.0

interface Serial0
 ip address 6.0.0.3 255.0.0.0

!

 router ospf 2
 network 12.0.0.0 0.255.255.255 area 2
 network 6.0.0.0 0.255.255.255 area 1
area 0 authentication message-digest

!--- This command enables MD5 authentication for area 0
!--- on the router.

area 1 virtual-link 1.1.1.1 message-digest-key 1 md5 cisco

!--- This command creates the virtual link to area 0 via
!--- the transit area 1 with MD5 authentication enabled.

If we use this as an example of a common misunderstanding concerning
the virtual-link in OSPF. One issue that stands out to me is the area
0 authentication message-digest

Notice that it is uses area 0 for the message digest and not the
transit area or the non-transit far side area. This is an issue that
may only be worth 1-2 points but it can cause a headache if we forget
it or worse are not aware of it. So how do we troubleshoot it. Since
Anthony and Joe have been nice enough to follow along, I will let them
explain the details of the problem. How it presents itself, and why we
the problem exists.

Blogs and organic groups at http://www.ccie.net
Received on Fri Sep 25 2009 - 19:19:43 ART